Challenge — Migrate Payroll Tracker to TypeScript

Objective

Take the JavaScript Payroll Tracker from Module 03 and migrate it fully to TypeScript.

Requirements

Types (40 points)

• Employee interface with all required fields and proper types
• PayrollState interface for the application state
• All function parameters and return types annotated
• No any types — noImplicitAny must pass
• strict: true in tsconfig — no errors

Utility Types (30 points)

• Use Omit<Employee, 'id' | 'addedAt'> for the create input type
• Use Partial<Employee> for the update input type
• Use Readonly<Employee> where employees should not be mutated
• Create a SortableField type using keyof Employee

Code (30 points)

• Separate files: types.ts, data.ts, render.ts, storage.ts, main.ts
• tsconfig.json with strict, noUncheckedIndexedAccess, noUnusedLocals
• Compiles with zero errors: npx tsc --noEmit

Expected Types

// src/types.ts

interface Employee {
  id: string;
  firstName: string;
  lastName: string;
  salary: number;
  department: string;
  addedAt: string;
}

type CreateEmployeeInput = Omit<Employee, 'id' | 'addedAt'>;
type UpdateEmployeeInput = Partial<Omit<Employee, 'id' | 'addedAt'>>;
type SortableField = keyof Pick<Employee, 'lastName' | 'salary' | 'department'>;

interface PayrollState {
  employees: Readonly<Employee>[];
  sortBy: SortableField;
  sortDir: 'asc' | 'desc';
}

Grading

Criteria	Points
All interfaces defined correctly	20
Utility types used properly	30
All functions typed (no implicit any)	20
tsc --noEmit passes	20
tsconfig strict mode	10
Total	100